The present invention relates to in situ extraction of minerals from subterranean deposits and pertains particularly to a method for extracting carbonaceous values from oil shale and other carbonaceous deposits.
It is well known that enormous deposits of subterranean carbonaceous deposits exist throughout the world today. Such deposits exist in the form of coal, oil shale, and tar sands, for example.
Commercial development of oil shale has lagged in this country because it could not compete with other sources of petroleum. Several proposals for the recovery of carbonaceous values have been made in the past. These proposals have one or more drawbacks which prevent them from being economically feasible.
In situ retorting is one proposal that continues to be of interest today. Several approaches to in situ retorting have been proposed. These approaches are generally exemplified by the following U.S. patents and the prior art cited therein: U.S. Pat. Nos. 1,913,395 issued June 13, 1933; 1,919,636 issued July 25, 1933; 2,481,051 issued Sept. 6, 1949; and 3,661,423 issued May 9, 1972.
These approaches involve breaking up the subterranean formation into rubble, and retorting the rubble. The rubble must be sufficiently packed so that combustion can be initiated in the deposit to drive the fluidized carbonaceous materials from the rubble. On the other hand, the rubble must have sufficient prosity or permeability to enable the fluids driven from the particles to flow therethrough for recovery.